Aqueous alteration processes in Jezero crater, Mars—implications for organic geochemistry

Abstract

The Perseverance rover landed in Jezero crater, Mars in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks, preserved in minerals related to both aqueous environments.

Alteration history of Séítah formation rocks inferred by PIXL x-ray fluorescence, x-ray diffraction, and multispectral imaging on Mars

“…We interpret this LZE component as indicating the presence of carbonate minerals or their hydrated forms. The regions in which we infer the presence of carbonate minerals correspond to direct detections of carbonate in colocated Raman spectroscopic measurements by the SHERLOC instrument (35). Moreover, the SuperCam instrument has also identified Mg/Fecarbonates in the Séítah formation (33), providing further confidence in our identification.…”

“…Inferred carbonate and sulfate minerals are consistent with Raman spectroscopic identification of these phases (35). SHERLOC did not detect perchlorate in Dourbes; however, it is not known whether SHERLOC sampled a spot with enough Cl-bearing phase to exclude its presence.…”

“…The detection of perchlorate by SHERLOC (35) and by Super-Cam (33) in overlying Máaz formation rocks containing more Cl than Dourbes (Séítah formation) but with similar saline mineral assemblages suggests that some of the Na-and Cl-bearing phase observed by PIXL could be NaClO 4 . Because perchlorate adds a large oxygen content relative to Cl alone, the XRF matrix effect is significantly different from that of NaCl.…”

Geological, multispectral, and meteorological imaging results from the Mars 2020 Perseverance rover in Jezero crater

“…S3). SuperCam, PIXL, and SHERLOC observations confirm the presence of olivine and pyroxenes with some alteration to carbonates and other phases (9,14,15). Such features are absent in the spectra of the pitted rocks comprising the Content member (Fig.…”

“…13 Joanneum Research, Graz 8010, Austria. 14 Western Washington University, Bellingham, WA 98225, USA. 15 German Aerospace Center (DLR), Berlin 12489, Germany.…”